The rapid advancement in modern wireless communication has put forward a much higher requirement on the reliability, the power handling capacity and the disturbance immunity of the communication systems.
Power amplifiers play a very important role in communication systems as they are widely used in microwave and communications engineering for converting a low power signal to a significantly higher power signal. In this regard, power amplifiers being able to operate in a wide range of power levels with high efficiency are particularly advantageous as the efficiency of the power amplifiers is crucially important for power saving in cellular infrastructures or extend working endurance for handsets.
Different types of power amplifiers are used depending on the applications and the amplification requirement. For example, modulated signals used in wireless communications nowadays are very complex as they are arranged to convey more information in a limited spectrum bandwidth. Consequently, these signals have very large peak-to-average power ratios (PAPRs). Power amplifiers that are able to provide power amplification and preserve the high efficiency for signals with large PAPRs are desirable for this application.